Well, the flip side of your argument is that since "his inputs are only time," then he only has a fixed amount of time to make money from. Whereas, as long as the car dealer can sell every car he buys, he just has to keep buying cars in order to increase his revenues. Clearly there's more to both of these statements than that, but that's the point!

In any case, roel_v is pointing out that revenue isn't a very good metric without more data to evaluate it.

I'd like you to provide an example of a business that doesn't scale :-)